In recent years, a model reduction method of closed CRN using the graph information encoded in the incidence matrix \(D\)  in (REF ) has been presented in [1]}. The reduction of model order is achieved by pruning the network graph and by replacing it with an equivalent or approximated reduced network graph. This approach is motivated by the Kron reduction method used in electrical networks (see, e.g. [2]}, [3]}, [4]}, and [5]}) and other complex networked systems, such as, [6]}. The use of the Kron reduction method enables the preservation of the network graph structure and has been shown to be effective in reducing state equations in a number of well-known biochemical reaction networks as presented in [1]} and in [8]}. Further work on this method can also be seen in [9]} and [10]}. There is also the method of structural reduction proposed by [11]} that can be applied to kinetic models with linear independent sub-CRNs consisting of linear reactions. Based on the detailed description of the linear sub-CRNs, the proposed method reduces them into a single reaction with distributed time delay. Therefore, one obtains a delayed CRN with conceivably different distributed time delays but with less complexes and reactions than the original model.
